Power amplifier, power amplifying method and radio communication apparatus

ABSTRACT

It is difficult that the impedance of the circuit part on the output side of an amplifying element at the frequency of a modulating wave is lower, and consequently, it is difficult to more effectively use the linearity of the amplifying element. The phase of a signal of the frequency of the modulating wave included in an amplified signal output from a FET is inverted by a difference frequency inverting circuit. The inverted signal of the frequency of the modulating wave and a signal of the frequency of a modulated wave included in an amplified signal output from a FET cancel each other out at the drain of the FET. At the drain end of the FET, the signal of the frequency of the modulating wave included in the amplified signal of the FET and a signal of the frequency of the modulating wave output from the FET cancel each other out.

BACKGROUND OF THE INVENTION

[0001] 1. Field of the Invention

[0002] The present invention relates to a power amplifier, a poweramplifying method amplifying high-frequency power, and a radiocommunication apparatus using the power amplifier.

[0003] 2. Description of the Prior Art

[0004] It is required that for size reduction and power saving, poweramplifiers used for portable telephone terminals and base stations havehigh-power and high-efficiency characteristics. In particular, whenwide-band transmission signals such as W-CDMA signals are handled, it isnecessary that power amplifiers have a wide band and little distortion.

[0005] However, the frequency spectrum of a modulated wave whose carrierwave is modulated by a modulating wave is normally distributed in a bandof approximately the frequency of the modulating wave. When a signal ofthe frequency of the modulated wave having such a frequency spectrum isinput to a power amplifier, because of the nonlinearity of an amplifyingelement such as a FET (field effect transistor) used for the poweramplifier, a second-order intermodulation distortion component thatappears at a frequency which is the difference between signals ofdifferent frequency components of the modulated wave is caused inaddition to an intermodulation distortion component.

[0006] Moreover, as mentioned above, to provide high-powercharacteristics, a FET arranged in parallel in a multifinger structureor a multiplicity of FETs combined in parallel to increase the gatewidth is used as the amplifying element of the power amplifier.

[0007] In such power amplifiers, when the impedance at the frequency ofthe modulating wave of the modulated wave on the output side of the FETis high to a degree, a second-order intermodulation distortion componentis caused that appears at the frequency which is the difference betweensignals of different frequency components of the modulated wave. Thefrequency of the second-order intermodulation distortion component isdistributed in the neighborhood of the frequency of the modulating wave,and the second-order intermodulation distortion component is again mixedwith the amplified signal at the drain electrode of the FET to makeintermodulation distortion worse. This indicates that the linearity ofthe FET is not effectively used.

[0008]FIG. 10 shows a conventional power amplifier 1113 being excellentin distortion characteristic. The power amplifier 1113 of FIG. 10comprises an input terminal 1101, matching circuits 1102, 1106 and 1110,a FET 1103, inductors 1104 and 1109, capacitors 1105 and 1108, aquarter-wave stripline 1107, an output terminal 1111, and a bias supplypower source terminal 1112.

[0009] The matching circuit 1102 is a circuit that matches the impedanceof the input terminal 1101 to that on the drain side of the FET 1103.

[0010] The inductor 1104 and the capacitor 1105 are circuits thatserially resonate at the frequency of the modulated wave. It is assumedthat the frequency of the modulated wave is, for example, 1 GHz and thefrequency of the modulating wave of the modulated wave is, for example,20 MHz.

[0011] The matching circuit 1106 is a circuit that matches the impedanceon the output side of the FET 1103 to that on side of the matchingcircuit 1110.

[0012] The double wave shorting circuit 1107 is a circuit that isshort-circuited for the harmonic of the frequency of the modulated wave,for example, a stripline.

[0013] The capacitor 1108, the inductor 1109 and the bias supplyterminal 1112 constitute a bias choke circuit that supplies a biasvoltage to the gate of the FET 1103.

[0014] The matching circuit 1110 is a circuit that matches the impedanceon the side of the matching circuit 1106 to that on the side of theoutput terminal 1111.

[0015] Next, the operation of the conventional power amplifier will bedescribed.

[0016] Since the signal of the frequency of the modulated wave (1 GHZ)is modulated by the modulating wave (20 MHz) of the modulated wave asmentioned above, the frequency of the signal of the frequency of themodulated wave is distributed, for example, in a band of approximately±20 MHz from the neighborhood of 1 GHz.

[0017] When input to the input terminal 1101, the signal of thefrequency of the modulated wave has its impedance matched by thematching circuit 1102 and is input to the gate of the FET 1103. Thedrain of the FET 1103 is supplied with a bias voltage by the bias chokecircuit constituted by the bias supply terminal 1112, the capacitor 1108and the inductor 1109.

[0018] Consequently, the signal of the frequency of the modulated waveinput to the gate of the FET 1103 is power-amplified by the FET 1103,and is output from the drain of the FET 1103 as an amplified signal.Because of the non-linearity of the FET 1103, the amplified signal alsoincludes a second-order intermodulation distortion component thatappears at a frequency which is the difference between signals ofdifferent frequency components of the modulated wave. The second-orderintermodulation distortion component is distributed in the neighborhoodof the frequency of the modulating wave (20 MHz).

[0019] The constant of a resonance circuit constituted by the inductor1104 and the capacitor 1105 is set so that the resonance circuitserially resonates in the neighborhood of the frequency of themodulating wave. Therefore, the impedance thereof is short-circuited atthe frequency of the modulating wave (20 MHz) and is high at thefrequency of the modulated wave (1 GHz).

[0020] Consequently, since the second-order intermodulation distortioncomponent included in the amplified component is short-circuited by theresonance circuit constituted by the inductor 1104 and the capacitor1105, the signal component that varies according to the frequency of themodulating wave is reduced in the voltage on the drain side of the FET1103. Consequently, the above-mentioned problem is reduced that thesecond-order intermodulation distortion component is mixed with theamplified signal at the drain to make intermodulation distortion worse.

[0021] The amplified signal output from the FET 1103 has itssecond-order intermodulation distortion component smoothed by theinductor 1104 and the capacitor 1105 as mentioned above, and has itsimpedance matched by the matching circuit 1106. The circuit constitutedby the double wave shorting circuit 1107 and the capacitor 1108 isshort-circuited by the high-order harmonic (signal having frequencyspectra of approximately 2 GHz and not less than 2 GHz) of the modulatedwave. Therefore, the high-order harmonic of the modulated wave includedin the amplified signal output from the matching circuit 1106 isshort-circuited by the circuit constituted by the double wave shortingcircuit 1107 and the capacitor 1108. The amplified signal having itshigh-order harmonic thus reduced has its impedance matched by thematching circuit 1110, and is output from the output terminal 1111.

[0022] As described above, it is necessary that power amplifiers usedfor a communication mode such as W-CDMA have a wide band and littledistortion. To achieve this, it is extremely important that theimpedance of the circuit part on the output side of the amplifyingelement at the frequency of the modulating wave (20 MHz) be lower thanthe impedance on the output side of the amplifying element at thefrequency (1 GHz) of the modulated wave as mentioned above.

[0023] Moreover, if the impedance of the circuit part on the output sidecan be reduced in a structure other than the structure used by theconventional power amplifier 1113 described with reference to FIG. 10,the degree of freedom of design will improve accordingly.

[0024] That is, a power amplifier is required in which the impedance ofthe circuit part on the output side of the amplifying element at thefrequency of the modulating wave can be reduced in a structure differentfrom that of the conventional power amplifier.

[0025] Moreover, while in the conventional power amplifier 1113described with reference to FIG. 10, the impedance at the frequency ofthe modulating wave (20 MHz) is made close to short-circuiting by theresonator constituted by the inductor 1104 and the capacitor 1105, inactuality, since some loss is caused at the frequency of the modulatingwave at the inductor 1104 and the capacitor 1105, it is difficult tocreate an ideal short-circuiting at the frequency of the modulatingwave. To reduce the loss, it is necessary to increase the physical sizesof the inductor 1104 and the capacitor 1105, and this increases the sizeof the power amplifier.

[0026] That is, it is difficult that the impedance of the circuit parton the output side of the amplifying element at the frequency of themodulating wave is lower, and consequently, it is difficult to moreeffectively use the linearity of the amplifying element.

[0027] In radio communication systems preceding a communication modesuch as W-CDMA, since the frequency band used for communication isnarrow, such a problem did not arise. However, in recent wide-bandsystems such as W-CDMA systems, it is an increasingly important problem.

SUMMARY OF THE INVENTION

[0028] In view of the above-mentioned problem, an object of the presentinvention is to provide a power amplifier, a power amplifying methodcapable of reducing the impedance of the circuit part on the output sideof the amplifying element at the frequency of the modulating wave in astructure different from that of the conventional power amplifier, and aradio communication apparatus.

[0029] Another object of the present invention is to provide a poweramplifier,a power amplifying method capable of lowering the impedance ofthe circuit part on the output side of the amplifying element at thefrequency of the modulating wave and of more effectively using thelinearity of the amplifying element, and a radio communicationapparatus.

[0030] The 1st invention of the present invention is a power amplifiercomprising:

[0031] a splitting circuit splitting a signal of a frequency of amodulated wave into two;

[0032] a first amplifying element having its input connected to oneoutput of said splitting circuit;

[0033] a second amplifying element having its input connected to theother output of said splitting circuit;

[0034] a combining circuit combining an output of said first amplifyingelement with an output of said second amplifying element to output acomposite signal;

[0035] a first filter having one end connected to the output of saidfirst amplifying element, said first filter not allowing the signal ofthe frequency of the modulated wave to pass therethrough and allowing asignal of a frequency band of a modulating wave of the signal of thefrequency of the modulated wave to pass therethrough;

[0036] a second filter having one end connected to the output of saidsecond amplifying element, said second filter not allowing the signal ofthe frequency of the modulated wave to pass therethrough and allowingthe signal of the frequency band of the modulating wave of the signal ofthe frequency of the modulated wave to pass therethrough; and

[0037] an phase inverting circuit connected between the other end ofsaid first filter and the other end of said second filter, said phaseinverting circuit allowing the signal of the frequency band of themodulating wave to pass therethrough while inverting a phase of thesignal of the frequency of the modulating wave.

[0038] The 2nd invention of the present invention is a power amplifieraccording to the 1st invention,

[0039] wherein said phase inverting circuit comprises an inductor and acapacitor.

[0040] The 3rd invention of the present invention is a power amplifieraccording to the 2nd invention,

[0041] wherein said phase inverting circuit comprises:

[0042] an inductor having one end connected to the other end of saidfirst filter and having its other end connected to the other end of saidsecond filter;

[0043] a first capacitor having one end connected to one end of saidinductor and having its other end grounded; and

[0044] a second capacitor having one end connected to the other end ofsaid inductor and having its other end grounded, and

[0045] wherein one end of said phase inverting circuit is one end ofsaid inductor, and the other end of said phase inverting circuit is theother end of said inductor.

[0046] The 4th invention of the present invention is a power amplifieraccording to the 1st invention, further comprising a bias choke circuitconnected at least one of said first filter, said second filter and saidphase inverting circuit, said bias choke circuit supplying a biasvoltage.

[0047] The 5th invention of the present invention is a power amplifieraccording to the 2nd invention,

[0048] wherein said phase inverting circuit comprises:

[0049] a first inductor;

[0050] a second inductor;

[0051] a first capacitor;

[0052] a second capacitor; and

[0053] a third capacitor,

[0054] wherein said first inductor has one end connected to the otherend of said first filter and has its other end connected to one end ofsaid second inductor, said second inductor has its other end connectedto the other end of said second filter, said first capacitor has one endconnected to the one end of said first inductor and has its other endgrounded, said second capacitor has one end connected to the other endof said first inductor and has its other end grounded, and said thirdcapacitor has one end connected to the other end of said second inductorand has its other end grounded, and

[0055] wherein one end of said phase inverting circuit is one end ofsaid first inductor and the other end of said phase inverting circuit isthe other end of said second inductor.

[0056] The 6th invention of the present invention is a power amplifieraccording to the 5th invention,

[0057] wherein said phase inverting circuit comprises:

[0058] a fourth inductor having one end connected to a bias supply andhaving its other end connected to the other end of said first inductor;and

[0059] a fourth capacitor connected to one end of said fourth inductorand having its other end grounded.

[0060] The 7th invention of the present invention is a power amplifiercomprising:

[0061] a splitting circuit splitting a signal of a frequency of amodulated wave into at least two;

[0062] a first amplifying element having its input connected to oneoutput of said splitting circuit;

[0063] a second amplifying element having its input connected to theother output of said splitting circuit;

[0064] a first filter having one end connected to an output of saidfirst amplifying element, said first filter not allowing the signal ofthe frequency of the modulated wave to pass therethrough and allowing asignal of a frequency band of a modulating wave of the modulated wave topass therethrough;

[0065] a second filter having one end connected to an output of saidsecond amplifying element, said second filter not allowing the signal ofthe frequency of the modulated wave to pass therethrough and allowingthe signal of the frequency band of the modulating wave to passtherethrough; and

[0066] an inverting amplifier having its output connected to the otherend of said first filter and having its input connected to the other endof the second filter, said inverting amplifier amplifying the signal ofthe frequency band of the modulating wave while inverting a phase of thesignal of the frequency band of the modulating wave,

[0067] wherein at least said output of said first amplifying element isoutput to an outside.

[0068] The 8th invention of the present invention is a power amplifiercomprising:

[0069] a splitting circuit splitting a signal of a frequency of amodulated wave into a number N (N is an integer not less than 3);

[0070] a number (N−1) of first amplifying elements having their inputsconnected to a number (N−1) of outputs of a number N of outputs of saidsplitting circuit;

[0071] a second amplifying element having its input connected to anoutput of said splitting circuit other than the number (N−1) of outputsof said splitting circuit;

[0072] a first filter having one end connected to inputs of a (N−1)splitting circuit splitting its input into a number (N−1) and havingtheir outputs connected to outputs of said number (N−1) of firstamplifying elements, said first filter not allowing the signal of thefrequency of the modulated wave to pass therethrough and allowing asignal of a frequency band of a modulating wave of the modulated wave topass therethrough;

[0073] a second filter having one end connected to an output of saidamplifying element, said second filter not allowing the signal of thefrequency of the modulated wave to pass therethrough and allowing thesignal of the frequency band of the modulating wave to passtherethrough;

[0074] an inverting amplifier having its input connected to the otherend of said second filter and having its output connected to the otherend of said first filter, said inverting amplifier amplifying the signalof the frequency band of the modulating wave while inverting a phase ofthe signal of the frequency band of the modulating wave; and

[0075] a combining circuit combining at least the outputs of said number(N−1) of first amplifying elements to output a composite signal.

[0076] The 9th invention of the present invention is a power amplifiercomprising:

[0077] a splitting circuit splitting a signal of a frequency of amodulated wave into a number N (N is an integer not less than 3);

[0078] a number (N−1) of first amplifying elements having their inputsconnected to a number (N−1) of outputs of a number N of outputs of thesplitting circuit;

[0079] a second amplifying element having its input connected to anoutput of said splitting circuit other than the number (N−1) of outputsof said splitting circuit;

[0080] a number (N−1) of first filters having one ends connected tooutputs of said number (N−1) of first amplifying elements, said firstfilters not allowing the signal of the frequency of the modulated waveto pass therethrough and allowing a signal of a frequency band of amodulating wave of the modulated wave to pass therethrough;

[0081] a second filter having one end connected to an output of saidsecond amplifying element, said second filter not allowing the signal ofthe frequency of the modulated wave to pass therethrough and allowingthe signal of the frequency band of the modulating wave to passtherethrough;

[0082] an inverting amplifier having its input connected to the otherend of said second filter, said inverting amplifier amplifying thesignal of the frequency band of the modulating wave while inverting aphase of the signal of the frequency band of the modulating wave; and

[0083] a combining circuit combining at least the outputs of said number(N−1) of first amplifying elements to output a composite signal,

[0084] wherein said other ends of said number (N−1) of first filters areconnected to the number (N−1) of outputs of a (N−1) splitting circuitsplitting its input into a number (N−1) and connected to an output ofsaid inverting amplifier.

[0085] The 10th invention of the present invention is a power amplifiercomprising:

[0086] a splitting circuit splitting a signal of a frequency of amodulated wave into a number N (N is an integer not less than 3);

[0087] a number (N−1) of first amplifying elements having their inputsconnected to a number (N−1) of outputs of a number N of outputs of saidsplitting circuit;

[0088] a second amplifying element having its input connected to anoutput of said splitting circuit other than the number (N−1) of outputsof said splitting circuit;

[0089] a number (N−1) of first filters having one ends connected tooutputs of said number (N−1) of first amplifying elements, said firstfilters not allowing the signal of the frequency of the modulated waveto pass therethrough and allowing a signal of a frequency band of amodulating wave of the modulated wave to pass therethrough;

[0090] a second filter having one end connected to an output of saidsecond amplifying element, said second filter not allowing the signal ofthe frequency of the modulated wave to pass therethrough and allowingthe signal of the frequency band of the modulating wave to passtherethrough;

[0091] a number (N−1) of inverting amplifiers having their outputsconnected to the other ends of said number (N−1) of first filters andhaving their inputs connected to the number (N−1) of outputs of a (N−1)splitting circuit splitting its input into a number (N−1) and havingtheir inputs connected to the other end of said second filter, saidinverting amplifiers amplifying the signal of the frequency band of themodulating wave while inverting a phase of the signal of the frequencyband of the modulating wave; and

[0092] a combining circuit combining at least the outputs of said number(N−1) of first amplifying elements to output a composite signal.

[0093] The 11th invention of the present invention is a power amplifiercomprising:

[0094] a splitting circuit splitting a signal of a frequency of amodulated wave into a number N (N is an integer not less than 3);

[0095] a number (N−1) of first amplifying elements having their inputsconnected to a number (N−1) of outputs of a number N of outputs of saidsplitting circuit;

[0096] a second amplifying element having its input connected to anoutput of said splitting circuit other than the number (N−1) of outputsof said splitting circuit;

[0097] a number (N−1) of first filters having one ends connected tooutputs of said number (N−1) of first amplifying elements, said firstfilters not allowing the signal of the frequency of the modulated waveto pass therethrough and allowing a signal of a frequency band of amodulating wave of the modulated wave to pass therethrough;

[0098] a number (N−1) of inverting amplifiers having their outputsconnected to the other ends of said number (N−1) of first filters, saidinverting amplifiers amplifying the signal of the frequency band of themodulating wave while inverting a phase of the signal of the frequencyband of the modulating wave;

[0099] a number (N−1) of second filters having one end connected toinputs of said number (N−1) of inverting amplifiers and having its otherend connected to the number (N−1) of outputs of a (N−1) splittingcircuits splitting its input into a number (N−1) and connected to anoutput of said second amplifying element, said second filters notallowing the signal of the frequency of the modulated wave to passtherethrough and allowing the signal of the frequency band of themodulating wave to pass therethrough; and

[0100] a combining circuit combining at least the outputs of said number(N−1) of first amplifying elements to output a composite signal.

[0101] The 12th invention of the present invention is a power amplifieraccording to any one of the 7th to 11th inventions,

[0102] wherein said output of said second amplifying element isterminated.

[0103] The 13th invention of the present invention is a power amplifieraccording to the 12th invention,

[0104] wherein that said output of said second amplifying element isterminated means that a terminating resistor is connected to the outputof said second amplifying element or that a terminating load comprisinga capacitor and/or an inductor is connected to the output of said secondamplifying element.

[0105] The 14th invention of the present invention is a power amplifieraccording to any one of the 7th to 11th inventions,

[0106] wherein said second amplifying element is smaller in amplifyingelement size than said first amplifying element.

[0107] The 15th invention of the present invention is a power amplifiercomprising a plurality of power amplifiers according to any one of the1st to 6th and 8th to 11th inventions,

[0108] wherein said splitting circuits of said power amplifiers arereplaced with one common element, and the same signal of the frequencyof the modulated wave is input, and

[0109] wherein said combining circuits of said power amplifiers arereplaced with one common element, and outputs one output signalgenerated by signal combination.

[0110] The 16th invention of the present invention is a power amplifiercomprising:

[0111] a plurality of power amplifiers according to the 7th invention;and

[0112] a combining circuit generating by signal combination an output tobe output to an outside of said power amplifiers, and outputting theoutput,

[0113] wherein said splitting circuits of said power amplifiers arereplaced with one common element, and the same signal of the frequencyof the modulated wave is input.

[0114] The 17th invention of the present invention is a power amplifierhaving a multilayer dielectric substrate where the power amplifieraccording to any one of the 1st to 11th inventions is formed.

[0115] The 18th invention of the present invention is a power amplifieraccording to the 17th invention,

[0116] wherein said multilayer dielectric substrate comprises: asemiconductor substrate disposed thereabove; and a multilayer dielectricsubstrate disposed below said semiconductor substrate.

[0117] The 19th invention of the present invention is a power amplifieraccording to the 18th invention, comprising an internal matchingsubstrate in which said multilayer dielectric substrate is disposed.

[0118] The 20th invention of the present invention is a power amplifieraccording to any one of the 1st to 11th inventions,

[0119] wherein a frequency of the signal of the frequency of themodulated wave is not more than a thousand times a frequency band of thesignal of the frequency band of the modulating wave.

[0120] The 21st invention of the present invention is a power amplifieraccording to any one of the 1st to 11th inventions,

[0121] wherein said first filter and said second filter allow a harmoniccomponent of the signal of the frequency of the modulating wave to passtherethrough.

[0122] The 22nd invention of the present invention is a radiocommunication apparatus having at least a transmitting circuitoutputting a transmission wave,

[0123] wherein said power amplifier according to any one of the 1st to11th inventions is used for said transmitting circuit.

[0124] The 23rd invention of the present invention is a power amplifyingmethod comprising the steps of:

[0125] a splitting step splitting a signal of a frequency of a modulatedwave into two;

[0126] a first amplifying step having its input connected to one outputof said splitting step and amplifying its input;

[0127] a second amplifying step having its input connected to the otheroutput of said splitting step and amplifying its input;

[0128] a combining step combining an output of said first amplifyingstep with an output of said second amplifying step to output a compositesignal;

[0129] a first filtering step having one end connected to the output ofsaid first amplifying step, said first filtering step not allowing thesignal of the frequency of the modulated wave to pass therethrough andallowing a signal of a frequency band of a modulating wave of the signalof the frequency of the modulated wave to pass therethrough;

[0130] a second filtering step having one end connected to the output ofsaid second amplifying step, said second filtering step not allowing thesignal of the frequency of the modulated wave to pass therethrough andallowing the signal of the frequency band of the modulating wave of thesignal of the frequency of the modulated wave to pass therethrough; and

[0131] an phase inverting step connected between the other end of saidfirst filtering step and the other end of said second filtering step,said phase inverting step allowing the signal of the frequency band ofthe modulating wave to pass therethrough while inverting a phase of thesignal of the frequency of the modulating wave.

[0132] The 24th invention of the present invention is a power amplifyingmethod comprising the steps of:

[0133] a splitting step splitting a signal of a frequency of a modulatedwave into at least two;

[0134] a first amplifying step having its input connected to one outputof said splitting step and amplifying its input;

[0135] a second amplifying step having its input connected to the otheroutput of said splitting step and amplifying its input;

[0136] a first filtering step having one end connected to an output ofsaid first amplifying step, said first filtering step not allowing thesignal of the frequency of the modulated wave to pass therethrough andallowing a signal of a frequency band of a modulating wave of themodulated wave to pass therethrough;

[0137] a second filtering step having one end connected to an output ofsaid second amplifying step, said second filtering step not allowing thesignal of the frequency of the modulated wave to pass therethrough andallowing the signal of the frequency band of the modulating wave to passtherethrough; and

[0138] an inverting amplifying step having its output connected to theother end of said first filtering step and having its input connected tothe other end of the second filtering step, said inverting amplifyingstep amplifying the signal of the frequency band of the modulating wavewhile inverting a phase of the signal of the frequency band of themodulating wave,

[0139] wherein at least said output of said first amplifying step isoutput to an outside.

[0140] The 25th invention of the present invetion is a power amplifyingmethod comprising the steps of:

[0141] a splitting step splitting a signal of a frequency of a modulatedwave into a number N (N is an integer not less than 3);

[0142] a number (N−1) of first amplifying steps having their inputsconnected to a number (N−1) of outputs of a number N of outputs of saidsplitting step and amplifying their inputs;

[0143] a second amplifying step having its input connected to an outputof said splitting step other than the number (N−1) of outputs of saidsplitting step and amplifying its input;

[0144] a first filtering step having one end connected to inputs of a(N−1) splitting step splitting its input into a number (N−1) and havingtheir outputs connected to outputs of said number (N−1) of firstamplifying steps, said first filter not allowing the signal of thefrequency of the modulated wave to pass therethrough and allowing asignal of a frequency band of a modulating wave of the modulated wave topass therethrough;

[0145] a second filtering step having one end connected to an output ofsaid amplifying step, said second filtering step not allowing the signalof the frequency of the modulated wave to pass therethrough and allowingthe signal of the frequency band of the modulating wave to passtherethrough;

[0146] an inverting amplifying step having its input connected to theother end of said second filtering step and having its output connectedto the other end of said first filtering step, said inverting amplifyingstep amplifying the signal of the frequency band of the modulating wavewhile inverting a phase of the signal of the frequency band of themodulating wave; and

[0147] a combining step combining at least the outputs of said number(N−1) of first amplifying steps to output a composite signal.

[0148] The 26th invention of the present invention is a power amplifyingmethod comprising the steps of:

[0149] a splitting step splitting a signal of a frequency of a modulatedwave into a number N (N is an integer not less than 3);

[0150] a number (N−1) of first amplifying steps having their inputsconnected to a number (N−1) of outputs of a number N of outputs of thesplitting circuit and amplifying their inputs;

[0151] a second amplifying step having its input connected to an outputof said splitting step other than the number (N−1) of outputs of saidsplitting step and amplifying its input;

[0152] a number (N−1) of first filtering steps having one ends connectedto outputs of said number (N−1) of first amplifying steps, said firstfiltering steps not allowing the signal of the frequency of themodulated wave to pass therethrough and allowing a signal of a frequencyband of a modulating wave of the modulated wave to pass therethrough;

[0153] a second filtering step having one end connected to an output ofsaid second amplifying step, said second filtering step not allowing thesignal of the frequency of the modulated wave to pass therethrough andallowing the signal of the frequency band of the modulating wave to passtherethrough;

[0154] an inverting amplifying step having its input connected to theother end of said second filtering step, said inverting amplifying stepamplifying the signal of the frequency band of the modulating wave whileinverting a phase of the signal of the frequency band of the modulatingwave; and

[0155] a combining step combining at least the outputs of said number(N−1) of first amplifying steps to output a composite signal,

[0156] wherein said other ends of said number (N−1) of first filteringstep are connected to the number (N−1) of outputs of a (N−1) splittingstep splitting its input into a number (N−1) and connected to an outputof said inverting amplifying step.

[0157] The 27th invention of the present invention is a power amplifyingmethod comprising the steps of:

[0158] a splitting step splitting a signal of a frequency of a modulatedwave into a number N (N is an integer not less than 3);

[0159] a number (N−1) of first amplifying steps having their inputsconnected to a number (N−1) of outputs of a number N of outputs of saidsplitting circuit and amplifying their inputs;

[0160] a second amplifying step having its input connected to an outputof said splitting circuit other than the number (N−1) of outputs of saidsplitting circuit and amplifying its input;

[0161] a number (N−1) of first filtering steps having one ends connectedto outputs of said number (N−1) of first amplifying steps, said firstfiltering steps not allowing the signal of the frequency of themodulated wave to pass therethrough and allowing a signal of a frequencyband of a modulating wave of the modulated wave to pass therethrough;

[0162] a second filtering step having one end connected to an output ofsaid second amplifying step, said second filtering step not allowing thesignal of the frequency of the modulated wave to pass therethrough andallowing the signal of the frequency band of the modulating wave to passtherethrough;

[0163] a number (N−1) of inverting amplifying steps having their outputsconnected to the other ends of said number (N−1) of first filteringsteps and having their inputs connected to the number (N−1) of outputsof a (N−1) splitting step splitting its input into a number (N−1) andhaving their inputs connected to the other end of said second filter,said inverting amplifying step amplifying the signal of the frequencyband of the modulating wave while inverting a phase of the signal of thefrequency band of the modulating wave; and

[0164] a combining step combining at least the outputs of said number(N−1) of first amplifying steps to output a composite signal.

[0165] The 28th invention of the present invention is a power amplifyingstep comprising the steps of:

[0166] a splitting step splitting a signal of a frequency of a modulatedwave into a number N (N is an integer not less than 3);

[0167] a number (N−1) of first amplifying steps having their inputsconnected to a number (N−1) of outputs of a number N of outputs of saidsplitting step and amplifying their inputs;

[0168] a second amplifying step having its input connected to an outputof said splitting step other than the number (N−1) of outputs of saidsplitting step and amplifying its input;

[0169] a number (N−1) of first filtering steps having one ends connectedto outputs of said number (N−1) of first amplifying steps, said firstfiltering steps not allowing the signal of the frequency of themodulated wave to pass therethrough and allowing a signal of a frequencyband of a modulating wave of the modulated wave to pass therethrough;

[0170] a number (N−1) of inverting amplifying steps having their outputsconnected to the other ends of said number (N−1) of first filteringsteps, said inverting amplifying steps amplifying the signal of thefrequency band of the modulating wave while inverting a phase of thesignal of the frequency band of the modulating wave;

[0171] a number (N−1) of second filtering steps having one end connectedto inputs of said number (N−1) of inverting amplifying step and havingits other end connected to the number (N−1) of outputs of a (N−1)splitting step splitting its input into a number (N−1) and connected toan output of said second amplifying element, said second filtering stepsnot allowing the signal of the frequency of the modulated wave to passtherethrough and allowing the signal of the frequency band of themodulating wave to pass therethrough; and

[0172] a combining step combining at least the outputs of said number(N−1) of first amplifying steps to output a composite signal.

BRIEF DESCRIPTION OF THE DRAWINGS

[0173]FIG. 1 is a view showing the structure of a power amplifieraccording to a first embodiment of the present invention;

[0174]FIG. 2 is a view showing a detailed structure of the part of adifference frequency phase inverting circuit and double waveshorting/bias choke circuits of the power amplifier according to thefirst embodiment of the present invention;

[0175]FIG. 3 is a view showing a detailed structure of the part of thedifference frequency phase inverting circuit and the double waveshorting/bias choke circuits of the power amplifier according to thefirst embodiment of the present invention;

[0176]FIG. 4 is a view showing the structure of a power amplifieraccording to a second embodiment of the present invention;

[0177]FIG. 5 is a view showing an example in which the power amplifieraccording to the first embodiment of the present invention is formedwithin a multilayer dielectric substrate;

[0178]FIG. 6 is a view showing an example in which the power amplifieraccording to the first embodiment of the present invention is formed ondielectric layers disposed on a semiconductor substrate;

[0179]FIG. 7 is a view showing an example in which the power amplifieraccording to the first embodiment of the present invention is containedin a high-frequency ceramic package;

[0180]FIG. 8 is a view showing an example in which the power amplifieraccording to the second embodiment of the present invention is formedwithin a multilayer dielectric substrate;

[0181]FIG. 9 is a view showing the structure of a radio circuit in thefirst and the second embodiments of the present invention; and

[0182]FIG. 10 is a view showing the structure of the conventional poweramplifier being excellent in distortion characteristic.

EXPLANATION OF REFERENCE NUMERALS

[0183]1 Oscillator

[0184]2 Oscillator

[0185]3 Modulator

[0186]4 Mixer

[0187]5 Power amplifier

[0188]6 Duplexer

[0189]7 Antenna

[0190]21 Input terminal

[0191]22 Matching circuit/splitting circuit

[0192]23 a FET

[0193]23 b FET

[0194]24 a Double wave shorting/bias choke circuit

[0195]24 b Double wave shorting/bias choke circuit

[0196]25 a Capacitor

[0197]25 b Capacitor

[0198]26 Difference frequency phase inverting circuit

[0199]27 a Capacitor

[0200]27 b Capacitor

[0201]28 Combining circuit/matching circuit

[0202]29 Output terminal

[0203]41 Matching circuit/splitting circuit

[0204]42 a FET

[0205]42 b FET

[0206]42 c FET

[0207]45 a Inverting amplifier

[0208]42 b Inverting amplifier

DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0209] Hereinafter, embodiments of the present invention will bedescribed.

[0210] (First Embodiment)

[0211]FIG. 1 shows the structure of a power amplifier 61 according to afirst embodiment of the present invention.

[0212] The power amplifier 61 of FIG. 1 is used, for example, as a poweramplifier 5 of a radio circuit 63 shown in FIG. 9.

[0213] First, the radio circuit 63 of FIG. 9 will be briefly described.

[0214] The radio circuit 63 comprises oscillators 1 and 2, a modulator3, mixers 4 and 9, the power amplifier 5, a low-noise amplifier 8, aduplexer 6 and an antenna 7.

[0215] The modulator 3 is a quadrature modulator that modulates thesignal output from the oscillator 1 with a baseband I signal and abaseband Q signal generated by a non-illustrated baseband portion. Inthe description given below, the frequency of the baseband I signal andthe baseband Q signal will be called the frequency of the modulatingwave, and it is assumed that the frequency of the modulating wave is,for example, 20 MHz.

[0216] The mixer 4 is a circuit that mixes the signal modulated by themodulator 3 with the signal output from the oscillator 2 into a signalof a transmission frequency.

[0217] In the description given below, the transmission frequency willbe called the frequency of the modulated wave, and it is assumed thatthe frequency of the modulated wave is, for example, 1 GHz. Moreover, asin the prior art, the frequency of the signal of the frequency of themodulated wave is distributed in a band of approximately ±20 MHz, whichis the modulating frequency, from the neighborhood of 1 GHz.

[0218] The power amplifier 5 is a circuit that amplifies the power ofthe signal of the transmission frequency, that is, the signal of thefrequency of the modulated wave, and outputs the amplified signal to theduplexer 6.

[0219] The duplexer 6 is a circuit that directs the amplified signal tothe antenna 7 and directs the reception signal received by the antenna 7to the low-noise amplifier 8.

[0220] The low-noise amplifier 8 is a circuit that amplifies thereception signal output from the duplexer 6.

[0221] The mixer 9 is a circuit that mixes the signal output from thelow-noise amplifier 8 with the signal output from the oscillator 2 intoa signal of an intermediate frequency.

[0222] A filter 10 is a circuit that reduces the unnecessary frequencycomponent of the signal of the intermediate frequency.

[0223] A demodulator 11 is a quadrature demodulator that combines thesignal of the intermediate frequency with the signal output from theoscillator 1 to thereby restore the baseband I signal and the baseband Qsignal.

[0224] The radio circuit 63 as described above is used for portabletelephone terminals using a communication mode such as W-CDMA and as theradio circuits of base stations of the portable telephone terminals. Byusing the power amplifier 61 of FIG. 1 as the power amplifier 5 of theradio circuit 63, a radio circuit 63 can be realized that is excellentin distortion characteristic over a wide band and consumes only a smallamount of power. The power amplifier 61 of FIG. 1 used as the poweramplifier 5 of the radio circuit 63 will be described.

[0225] In FIG. 1, to the input terminal 21 of the power amplifier 61,the input of a matching circuit/splitting circuit 22 is connected, andto the two outputs of the matching circuit/splitting circuit 22, thegate of a FET 23 a and the gate of a FET 23 b are connected. The drainof the FET 23 a is connected to one input of a combiningcircuit/matching circuit 28 through a capacitor 27 a for interruptingdirect current, and the drain of the FET 23 b is connected to the otherinput of the combining circuit/matching circuit 28 through a capacitor27 b for interrupting direct current. The output of the combiningcircuit/matching circuit 28 is connected to an output terminal 29.

[0226] The sources of the FET 23 a and the FET 23 b are both grounded.To the drain of the FET 23 a, one end of a double wave shorting/biaschoke circuit 24 a is connected. Likewise, to the drain of the FET 24 a,one end of a double wave shorting/bias choke circuit 24 b is connected.

[0227] Between the other end of the double wave shorting/bias chokecircuit 24 a and the other end of the double wave shorting/bias chokecircuit 24 b, a difference frequency phase inverting circuit 26 isconnected. To one end of the difference frequency phase invertingcircuit 26, one end of a capacitor 25 a for bypassing a double wave isconnected, and the other end of the capacitor 25 a is grounded.Likewise, to the other end of the difference frequency phase invertingcircuit 26, one end of a capacitor 25 b for bypassing a double wave isconnected, and the other end of the capacitor 25 b is grounded.

[0228] The input terminal 21 is a terminal to which the signal of thefrequency of the modulated wave, which is the input signal, is input.The output terminal 29 is a terminal from which the amplified signal,which is the output signal, is output.

[0229] The matching circuit/splitting circuit 22 is a circuit thatmatches the impedance on the input terminal side with each of theimpedances on the gate sides of the FETs 23 a and 24 b, and splits intotwo the signal of the frequency of the modulated wave input from theinput terminal 21 and inputs the split signals to the gates of the FETs23 a and 23 b.

[0230] The FET 23 a and the FET 23 b are amplifying elements thatamplify the power of the signal of the frequency of the modulated waveinput to the gates thereof.

[0231] The double wave shorting/bias choke circuit 24 a is a circuithaving a function of a filter that does not allow the signal of thefrequency of the modulated wave (signal of a frequency of approximately1 GHz) to pass therethrough and allows the signal of the frequency ofthe modulating wave (signal of a frequency of approximately 20 MHz) topass therethrough, a function of short-circuiting the impedance at thefrequency of the high-order harmonic of the frequency of the modulatedwave, and a function of a bias choke circuit that supplies a biasvoltage to the drain of the FET 23 a.

[0232] Likewise, the double wave shorting/bias choke circuit 24 b is acircuit having a function of a filter that does not allow the signal ofthe frequency of the modulated wave (signal of a frequency ofapproximately 1 GHz) to pass therethrough and allows the signal of thefrequency of the modulating wave (signal of a frequency of approximately20 MHz) to pass therethrough, a function of short-circuiting theimpedance at the frequency of the high-order harmonic of the frequencyof the modulated wave, and a function of a bias choke circuit thatsupplies a bias voltage to the drain of the FET 23 a.

[0233] The difference frequency phase inverting circuit 26 is a circuitthat, when the signal of the frequency of the modulating wave passestherethrough, inverts the phase of the signal of the frequency of themodulating wave.

[0234] The combining circuit/matching circuit 28 is a circuit thatmatches each of the impedances on the sides of the capacitors 27 a and27 b with the impedance on the side of the output terminal 29, andcombines the amplified signal having passed through the capacitor 27 awith the amplified signal having passed through the capacitor 27 b andoutputs the composite signal to the output terminal 29.

[0235]FIG. 2 shows a detailed structure of the part of the double waveshorting/bias choke circuit 24 a, the double wave shorting/bias chokecircuit 24 b and the difference frequency phase inverting circuit 26.

[0236] That is, the difference frequency phase inverting circuit 26comprises capacitors 31 and 32 and an inductor 30. One end of theinductor 30 is connected to the other end of the double waveshorting/bias choke circuit 24 a, and the other end of the inductor 30is connected to the other end of the double wave shorting/bias chokecircuit 24 b. To one end of the inductor 30, one end of the capacitor 31is connected, and the other end of the capacitor 31 is grounded. To theother end of the inductor 30, one end of the capacitor 32 is connected,and the other end of the capacitor 32 is grounded. The capacitances ofthe capacitors 31 and 32 and the inductance of the inductor 30 areadjusted so that the phase of the signal of the frequency of themodulating wave (20 MHz) having passed through the difference frequencyphase inverting circuit 26 is inverted 180 degrees.

[0237] The double wave shorting/bias choke circuits 24 a and 24 b eachhave a structure such that the output end of a non-illustrated biassupply terminal is connected to a stripline having a length ¼ thewavelength of the frequency of the modulated wave and the input end ofthe bias supply terminal is connected to a bias supply terminalsupplying a direct current bias.

[0238] Next, the operation of the present embodiment structured asdescribed above will be described.

[0239] Assume now that the signal of the frequency of the modulated waveis input to the input terminal 21. As mentioned above, this signal is asignal of a frequency of 1 GHz where the frequency is distributed in aband of approximately the frequency of the modulating wave (20 MHz).

[0240] The signal of the frequency of the modulated wave input to theinput terminal 21 is split into two by the matching circuit/splittingcircuit 22, and the two split signals of the frequency of the modulatedwave are input to the gate of the FET 23 a and the gate of the FET 24 b.At this time, the matching circuit/splitting circuit 22 matches theimpedance on the side of the input terminal 21 to each of the impedanceson the gate sides of the FET 23 a and the FET 23 b.

[0241] To the drain of the FET 23 a, a direct current bias is suppliedfrom the double wave shorting/bias choke circuit 24 a. The signal of thefrequency of the modulated wave output to the gate of the FET 23 a isamplified by the FET 23 a and output to the drain of the FET 23 a.

[0242] Likewise, to the drain of the FET 23 b, a direct current bias issupplied from the double wave shorting/bias choke circuit 24 b. Thesignal of the frequency of the modulated wave output to the gate of theFET 23 b is amplified by the FET 23b and output to the drain of the FET23 b.

[0243] While the FET 23 a and the FET 23 b have a linear characteristic,a nonlinear characteristic is conspicuous during high-efficiencyoperation. Because of the nonlinear characteristic, the amplified signalwhich is the signal of the frequency of the modulated wave amplified bythe FET 23 a includes a distortion component. Examples of thisdistortion component include a distortion component of the high-orderharmonic of the signal of the frequency of the modulated wave(distortion component of a frequency of not less than approximately 2GHz), a third-order intermodulation distortion component that appears ata frequency in the neighborhood of the frequency of the modulated wave(distortion component that appears in the neighborhood of 1 GHz) and asecond-order intermodulation distortion component having a frequencywhich is the difference between different frequency components of thesignal of the frequency of the modulated wave to be amplified(distortion component of a frequency of approximately 20 MHz).

[0244] The double wave shorting/bias choke circuit 24 a allows thesecond-order intermodulation distortion component, that is, the signalof the frequency of the modulating wave to pass therethrough, andshort-circuits the signal of the frequency of the high-order harmonic soas to be totally reflected. Moreover, since the impedance is high at thefrequency of the modulated wave, the double wave shorting/bias chokecircuit 24 a does not allow the signal of the frequency of the modulatedwave to pass therethrough. Therefore, when the amplified signalincluding such a distortion component as well is output from the drainof the FET 23 a, of the amplifier signal, the second-orderintermodulation distortion component is input to one end of the doublewave shorting/bias choke circuit 24 a, and the signal of the frequencyof the modulating wave passes through the double wave shorting/biaschoke circuit 24 a. On the other hand, the signal of the frequency ofthe modulating wave is input to the difference frequency phase invertingcircuit 26.

[0245] Of the amplified signal, the signal of the frequency of themodulated wave does not pass through the double wave shorting/bias chokecircuit 24 a and is output to one input of the combiningcircuit/matching circuit 28 through the capacitor 27 a.

[0246] The signal of the frequency of the modulating wave having passedthrough the double wave shorting/bias choke circuit 24 a has its phaseinverted 180 degrees by passing through the difference frequency phaseinverting circuit 26. That is, the capacitances of the capacitors 31 and32 and the inductance of the inductor 30 of the difference frequencyphase inverting circuit 26 are previously adjusted so that the phase ofthe frequency of the modulating wave having passed through thedifference frequency phase inverting circuit 26 is inverted 180 degrees.The signal of the frequency of the modulating wave having passed throughthe difference frequency phase inverting circuit 26 further passesthrough the double wave shorting/bias choke circuit 24 b to reach thedrain end of the FET 23 b. The phase of this signal of the frequency ofthe modulating wave and the phase of the signal of the frequency of themodulating wave which is the second-order intermodulation distortioncomponent included in the amplified component amplified by the FET 23 band output to the drain end of the FET 23 b are different from eachother by 180 degrees. Therefore, these two signals of the frequency ofthe modulating wave cancel each other out at the drain end of the FET 23b. Consequently, at the drain of the FET 23 b, since the signals of thefrequency of the modulating wave cancel each other out, intermodulationdistortion can be prevented from deteriorating due to the mixture of thesignal of the frequency of the modulating wave which is the second-orderintermodulation distortion component with the signal of the frequency ofthe modulated wave at the drain of the FET 23 b.

[0247] Likewise, the amplified signal at the FET 23 b has its phaseinverted by 180 degrees by the double wave phase inverting circuit 26,and reaches the drain end of the FET 23 a Since the phase of this signalof the frequency of the modulating wave is different by 180 degrees fromthe phase of the signal of the modulating frequency which is thesecond-order intermodulation distortion component included in theamplified signal output from the drain end of the FET 23 a, these twosignals of the frequency of the modulating wave cancel each other out atthe drain of the FET 23 a. Consequently, at the FET 23 a, as in the FET23 b, intermodulation distortion can be prevented from deteriorating dueto the mixture of the signal of the frequency of the modulating wavewith the signal of the frequency of the modulated wave at the drain.

[0248] Moreover, of the amplified signal output from the FET 23 b, thesignal of the frequency of the modulated wave does not pass through thedouble wave shorting/bias choke circuit 24 b and is output to the otherinput of the combining circuit/matching circuit 28 through the capacitor27 b.

[0249] The combining circuit/matching circuit 28 combines the signals ofthe modulating wave input to the two inputs with each other, and outputsthe composite signal to the output terminal 29. At this time, thecombining circuit/matching circuit 28 matches each of the impedances onthe sides of the capacitors 27 a and 27 b to the impedance on the sideof the output terminal 29.

[0250] The signal of the modulated wave thus amplified is output fromthe output terminal 29.

[0251] While in the present invention, the difference frequency phaseinverting circuit 26 and the double wave shorting/bias choke circuits 24a and 24 b are structured as shown in FIG. 2, the structure is notlimited thereto and may be as shown in FIG. 3.

[0252]FIG. 3 shows a structure in which double wave shorting circuits 64a and 64 b are used instead of the double wave shorting/bias chokecircuits 24 a and 24 b, a difference frequency phase inverting circuit66 is used instead of the difference wave phase inverting circuit 26,and a bias choke circuit is connected to the difference frequency phaseinverting circuit 66.

[0253] In FIG. 3, the double wave shorting circuits 64 a and 64 b areeach a stripline having a length ¼ the wavelength at the frequency ofthe modulated wave. The difference frequency phase inverting circuit 66comprises inductors 33 and 34 and capacitors 35, 36 and 37. One end ofthe inductor 33 is connected to the other end of the double waveshorting circuit 64 a, the other end of the inductor 33 is connected toone end of the inductor 34, and the other end of the inductor 34 isconnected to the other end of the double shorting circuit 64 b. To oneend of the inductor 33, one end of the capacitor 35 is connected, andthe other end of the capacitor 35 is grounded. To the other end of theinductor 33, one end of the capacitor 36 is connected, and the other endof the capacitor 36 is grounded. To the other end of the inductor 34,one end of the capacitor 37 is connected, and the other end of thecapacitor 37 is grounded.

[0254] The inductances of the inductors 33 and 34 and the capacitancesof the capacitors 35, 36 and 37 are previously adjusted so that, as inthe case of the difference frequency phase inverting circuit 26, whenthe signal of the frequency of the modulating wave passes through thedifference frequency phase inverting circuit 66, the phase of the signalis inverted 180 degrees.

[0255] The bias choke circuit has a structure such that one end of theinductor 38 and one end of the capacitor 39 are connected to a biassupply terminal 40, the other end of the capacitor 39 is grounded andthe other end of the inductor 38 is connected to the other end of theinductor 33.

[0256] When the circuit shown in FIG. 3 is used instead of the circuitshown in FIG. 2, a direct current bias can be supplied to the FET 23 aand the FET 23 b and the phase of the signal of the frequency of themodulating wave passing through the difference frequency phase invertingcircuit 66 can also be inverted 180 degrees. Consequently, equal effectsto those obtained when the circuit of FIG. 2 is used are obtained.

[0257] As described above, in the power amplifier 61 of the presentinvention, since the signals of the frequency of the modulating wavecancel each other out at the drain end of each of the FET 23 a and theFET 23 b, intermodulation distortion can be prevented from deterioratingdue to the mixture of the signal of the frequency of the modulating wavewith the signal of the frequency of the modulated wave at the drains.

[0258]FIG. 5 shows an example in which the power amplifier 61 of thepresent embodiment is formed within a dielectric lamination comprising alamination of dielectric substrates 71 to 76.

[0259] On the dielectric substrate 71, the following are formed: thematching circuit/splitting circuit 22; the FETs 23 a and 23 b; thecapacitors 27 a and 27 b formed as chip capacitors; and the combiningcircuit/matching circuit 28.

[0260] On the dielectric substrate 72 disposed below the dielectricsubstrate 71, a shield electrode is formed. On the dielectric substrate73 disposed below the dielectric substrate 72, the double waveshorting/bias choke circuits 24 a and 24 b and the inductor 30 areformed. Between the dielectric substrate 73 and grounded layers whichare the shield electrode of the dielectric substrate 72 and a shieldelectrode of the dielectric substrate 74, the bypass capacitors 25 a and25 b are formed.

[0261] On the dielectric substrate 74 disposed below the dielectricsubstrate 73, the shield electrode is formed. On the dielectricsubstrate 75 disposed below the dielectric substrate 73, the capacitors31 and 32 are formed. On the dielectric substrate 76 disposed below thedielectric substrate 75, a shield electrode is formed.

[0262]FIG. 6 shows an example in which the power amplifier 61 of thepresent embodiment is formed on dielectric layers on a semiconductorsubstrate.

[0263] On the semiconductor substrate 77, an insulating film such as apolyimide film is formed. On the semiconductor substrate 77, thefollowing are formed: the matching circuit/splitting circuit 22; theFETs 23 a and 23 b; and the combining circuit/matching circuit 28.

[0264] Below the semiconductor substrate 77, a dielectric substrate 78is formed. On the dielectric substrate 78, the double wave shorting/biaschoke circuits 24 a and 24 b and the capacitors 27 a and 27 b areformed. Between the dielectric substrate 78 and a grounded layer whichis a shield electrode of a dielectric substrate 79, the bypasscapacitors 25 a and 25 b are formed. Below the dielectric substrate 78,the dielectric substrate 79 on which the shield electrode is formed isformed, and below the dielectric substrate 79, a dielectric substrate 80is formed. On the dielectric substrate 80, the capacitors 31 and 32 andthe inductor 30 are formed.

[0265]FIG. 7 shows an example in which the power amplifier 61 of thepresent embodiment is contained in a high-frequency ceramic package. Theone shown in FIG. 7 is for high power and used for portable telephonebase stations. The power amplifier 61 of FIG. 7 uses the circuit of FIG.3.

[0266] A multilayer dielectric substrate where a semiconductor substrate83 a and dielectric substrates 83 b and 84 to 88 are laminated in thisorder is mounted on an internal matching substrate 82 disposed in thehigh-frequency package 81, and the input terminal 21, an output terminal20 and the bias supply terminal 40 are drawn out of the high-frequencypackage 81.

[0267] On the semiconductor substrate 83 a, the following are formed:the matching circuit/splitting circuit 22; the FETs 23 a and 23 b; thecapacitor 39; and the combining circuit/matching circuit 28. Below thedielectric substrate 83 b, the dielectric substrate 84 is formed. On thedielectric substrate 84, the capacitors 27 a and 27 b are formed.

[0268] Below the dielectric substrate 84, the dielectric substrate 85 onwhich a shield electrode is formed is formed. Below the dielectricsubstrate 85, the dielectric substrate 86 is formed. On the dielectricsubstrate 86, the inductors 38, 33 and 34 and the double waveshorting/bias choke circuits 64 a and 64 b are formed. Between thedielectric substrate 86 and a grounded layer which is the shieldelectrode of the dielectric substrate 85, the bypass capacitors 25 a and25 b are formed.

[0269] Below the dielectric substrate 86, the dielectric substrate 87 isformed. Between the dielectric substrate 87 and a grounded layer whichis a shield electrode of the dielectric substrate 88, the capacitors 35,36, 37 and 39 are formed. Below the dielectric substrate 87, thedielectric substrate 88 on which the shield electrode is formed isformed.

[0270] While in the present embodiment, the frequency of the signal ofthe frequency of the modulated wave is 1 GHz and the frequency band ofthe signal of the frequency of the modulating wave is 20 MHz, thepresent invention is not limited. As long as the frequency of the signalof the frequency of the modulated wave is not more than a thousand timesthe frequency band of the signal of the frequency band of the modulatingwave, intermodulation distortion can be more excellently improved in thepresent embodiment than in the prior art.

[0271] Examples of the case where the frequency of the signal of thefrequency of the modulated wave is not more than a thousand times thefrequency band of the signal of the frequency band of the modulatingwave as mentioned above include the following:

[0272] First, there is a case where CDMA 2000 is used as thecommunication mode. In this case, as the signal of the frequency of themodulated wave, a signal of a frequency of an 800 MHz band and a signalof a frequency of a 2 GHz band are used. When the signal of thefrequency of the 800 MHz band is used as the signal of the frequency ofthe modulated wave in CDMA 2000, the frequency band of the signal of thefrequency band of the modulating wave is 1.23 MHz, so that the frequencyof the signal of the frequency of the modulated wave is not more than athousand times the frequency band of the signal of the frequency band ofthe modulating wave. Consequently, intermodulation distortion can beexcellently improved.

[0273] Moreover, the 2 GHz band of CDMA 2000 is a frequency band usedspecifically for data communication, and a plurality of channels is usedto perform high-speed data communication. That is, for high-speedcommunication, data communication is performed by using a frequency bandcorresponding to a maximum of three channels, and when the frequencyband corresponding to a maximum of three channels is used, the frequencyband of the signal of the frequency band of the modulating wave is 3.69MHz. As described above, the 2 GHz band in CDMA 2000 is used when datacommunication is performed with a personal computer and a terminal wherethe functions of a PDA and a portable telephone are integrated. In thiscase, the frequency of the signal of the frequency of the modulated waveis also not more than a thousand times the frequency band of the signalof the frequency band of the modulating wave, so that intermodulationdistortion can be improved more excellently than in the prior art.

[0274] Moreover, in IEEE 802.11a which is a wireless LAN standard, a 5GHz band is used as the frequency of the signal of the frequency of themodulated wave, and the frequency band of the signal of the frequencyband of the modulating wave is 20 MHz, so that intermodulationdistortion can be excellently improved like in the above-describedcases.

[0275] Moreover, in so-called fourth-generation mobile communications,the 5 GHz band is used as the frequency of the signal of the frequencyof the modulated wave, and the frequency band of the signal of thefrequency band of the modulating wave is a 10 MHz band. Therefore, alsoin this case, since the frequency of the signal of the frequency of themodulated wave is not more than a thousand times the frequency band ofthe signal of the frequency band of the modulating wave, intermodulationdistortion can be more excellently improved than in the prior art.

[0276] Moreover, broadcasting stations and relay stations of digitaltelevision broadcasting use frequencies of 400 MHz to 700 MHz as thefrequency of the signal of the frequency of the modulated wave. Thefrequency band of the signal of the frequency band of the modulatingwave is 6 MHz. Therefore, also in this case, since the frequency of thesignal of the frequency of the modulated wave is not more than athousand times the frequency band of the signal of the frequency band ofthe modulating wave, intermodulation distortion can be more excellentlyimproved than in the prior art.

[0277] While in the present invention, the double wave shorting/biaschoke circuits short-circuit the impedance at the frequency of thehigh-order harmonic of the frequency of the modulated wave, they may bedesigned so as to allow the signal of the frequency of the -high-orderharmonic of the frequency of the modulated wave to pass therethrough. Inthis case, a more excellent characteristic is obtained as a poweramplifier.

[0278] As described above, according to the present invention, theoverall size of the circuit can be reduced by integrating the doublewave shorting/bias choke circuits 24 a and 24 b and the like, and thedifference frequency phase inverting circuit 26 with one another, thatis, integrating these circuits into one lamination.

[0279] (Second Embodiment)

[0280] Next, a second embodiment of the present invention will bedescribed.

[0281]FIG. 4 shows the structure of a power amplifier 62 according tothe second embodiment.

[0282] The power amplifier 62 of the present embodiment is used, forexample, as the power amplifier 5 of the radio circuit 63 of FIG. 9described in the first embodiment.

[0283] To an input terminal 21 of the power amplifier 62, the input of amatching circuit/splitting circuit 41 is connected. To the three outputsof the matching circuit/splitting circuit 41, the gate of a FET 42 a,the gate of a FET 42 b and the gate of a FET 42 c are connected,respectively.

[0284] The drain of the FET 42 a is connected to one of the two inputsof a combining circuit/matching circuit 28 through a capacitor 27 a forinterrupting direct current. The drain of the FET 42 c is connected tothe other input of the combining circuit/matching circuit 28 through acapacitor 27 b for interrupting direct current. The output of thecombining circuit/matching circuit 28 is connected to an output terminal29. The drain of the FET 42 b is terminated by a terminating resistor48.

[0285] The sources of the FETs 42 a, 42 b and 42 c are grounded. To thedrain of the FET 42 a, one end of a double wave shorting circuit 43 a isconnected. Likewise, to the drain of the FET 42 c, one end of a doublewave shorting circuit 43 d is connected. Moreover, to one output of anon-illustrated splitting circuit connected to the drain of the FET 42b, one end of a double wave shorting circuit 43 b is connected, and tothe other output of the splitting circuit, one end of a double waveshorting circuit 43 c is connected.

[0286] Between the other end of the double wave shorting circuit 43 aand the other end of the double wave shorting circuit 43 b, an invertingamplifier 45 a is connected. To the output and the input of theinverting amplifier 45 a, one end of a capacitor 44 a for bypassing adouble wave and one end of a capacitor 46 a for bypassing a double waveare connected, respectively. The other end of the capacitor 44 a and theother end of the capacitor 46 a are grounded.

[0287] Between the other end of the double wave shorting circuit 43 dand the other end of the double wave shorting circuit 43 c, an invertingamplifier 45 b is connected. To the output and the input of theinverting amplifier 45 b, one end of a capacitor 44 b for bypassing adouble wave and one end of a capacitor 46 b for bypassing a double waveare connected, respectively. The other end of the capacitor 44 b and theother end of the capacitor 46 b are grounded.

[0288] The input terminal 21 is, like that of the first embodiment, aterminal to which the signal of the frequency of the modulated wave,which is the input signal, is input. The output terminal 29 is aterminal from which the amplified signal, which is the output signal, isoutput.

[0289] The matching circuit/splitting circuit 42 is a circuit thatmatches the impedance on the side of the input terminal 21 with each ofthe impedances on the gate sides of the FETs 42 a, 42 b and 42 c, andsplits into three the signal of the frequency of the modulated waveinput from the input terminal 21 and inputs the split signals to thegates of the FETs 42 a, 42 b and 42 c.

[0290] The FETs 42 a, 42 b and 42 c are amplifying elements that amplifythe power of the signal of the frequency of the modulated wave input tothe gates thereof. It is assumed that the FET size of the FET 42 b issmaller than those of the FET 42 a and the FET 42 c. Moreover, it isassumed that the FET 42 a and the FET 42 c have the same FET size.

[0291] The double wave shorting circuits 43 a, 43 b, 43 c and 43 d arecircuits having a function of a filter that does not allow the signal ofthe frequency of the modulated wave (signal of a frequency ofapproximately 1 GHz) to pass therethrough and allows the signal of thefrequency of the modulating wave (signal of a frequency of approximately20 MHz) to pass therethrough, and a function of short-circuiting theimpedance at the frequency of the high-order harmonic of the frequencyof the modulated wave.

[0292] The inverting amplifiers 45 a and 45 b are circuits that amplifythe signal of the frequency of the modulating wave while inverting thephase thereof 180 degrees.

[0293] The combining circuit/matching circuit 28 is a circuit thatmatches each of the impedances on the sides of the capacitors 27 a and27 b with the impedance on the side of the output terminal 29, andcombines the amplified signal having passed through the capacitor 27 awith the amplified signal having passed through the capacitor 27 b andoutputs the composite signal to the output terminal 29.

[0294] Next, the operation of the present embodiment structured asdescribed above will be described.

[0295] Assume now that the signal of the frequency of the modulated waveis input to the input terminal 21. As mentioned above, this signal is asignal of a frequency of 1 GHz where the frequency is distributed in aband of approximately the frequency of the modulating wave (20 MHz).

[0296] The signal of the frequency of the modulated wave input to theinput terminal 21 is split into three by the matching circuit/splittingcircuit 41, and the three split signals of the frequency of themodulated wave are input to the gate of the FET 42 a, the gate of theFET 42 b and the gate of the FET 42 c from the outputs. At this time,the matching circuit/splitting circuit 41 matches the impedance on theside of the input terminal 21 to each of the impedances on the gatesides of the FETs 42 a, 42 b and 42 c.

[0297] The signals of the frequency of the modulated wave output to thegates of the FETs 42 a, 42 b and 42 c are amplified by the FETs 42 a, 42b and 42 c and output to the drains thereof.

[0298] While the FETs 42 a, 42 b and 42 c have a linear characteristiclike in the first embodiment, a nonlinear characteristic is conspicuousduring high-efficiency operation. Because of the nonlinearcharacteristic, the amplified signals which are the signals of thefrequency of the modulated wave amplified by the FETs 42 a, 42 b and 42c include a distortion component. Examples of this distortion componentinclude a distortion component of the high-order harmonic of the signalof the frequency of the modulated wave (distortion component of afrequency of not less than approximately 2 GHz) a third-orderintermodulation distortion component that appears at a frequency in theneighborhood of the frequency of the modulated wave (distortioncomponent that appears in the neighborhood of 1 GHz) and a second-orderintermodulation distortion component having a frequency which is thedifference between different frequency components of the signal of thefrequency of the modulated wave to be amplified (distortion component ofa frequency of approximately 20 MHz).

[0299] The double wave shorting circuits 43 a, 43 b, 43 c and 43 d allowthe second-order intermodulation distortion component, that is, thesignal of the frequency of the modulating wave to pass therethrough, andshort-circuit the signal of the frequency of the high-order harmonic soas to be totally reflected. Moreover, since the impedance is high at thefrequency of the modulated wave, the double wave shorting circuits 43 a,43 b, 43 c and 43 d do not allow the signal of the frequency of themodulated wave to pass therethrough.

[0300] Therefore, when the amplified signals including such a distortioncomponent as well are output from the drains of the FETs 42 a and 42 c,of the amplifier signals, the second-order intermodulation distortioncomponents pass through the double wave shorting circuits 43 a and 43 d,respectively.

[0301] On the other hand, when the amplified signal including such adistortion component is output from the drain of the FET 42 b, of theamplified signal, the second-order intermodulation distortion componentand the distortion component of the frequency of the high-order harmonicpass through the double wave shorting circuits 43 b and 43 c. Then, thesignal of the frequency of the high-order harmonic is bypassed to groundby the capacitors 44 a and 44 b for interrupting a double wave.Moreover, of the amplified signal, the signal of the frequency of themodulated wave does not pass through the double wave shorting circuits43 b and 43 c and is terminated by the terminating resistor 48.

[0302] The signal of the modulating frequency passes through the doublewave shorting circuits 43 b and 43 c to be input to the invertingamplifiers 45 a and 45 b. The inverting amplifiers 45 a and 45 b amplifythe input signals of the modulating frequency while inverting the phasesof the signals 180 degrees.

[0303] The signal of the modulating frequency amplified by the invertingamplifier 45 a passes through the double wave shorting circuit 43 a toreach the drain end of the FET 42 a. When passing through the doublewave shorting circuit 43 a, the signal of the frequency of themodulating wave is somewhat attenuated because of a loss at the doublewave shorting circuit 43 a.

[0304] The gain of the inverting amplifier 42 a is previously adjustedso that the amplitude of the signal output from the inverting amplifier45 a after inverted and amplified by the inverting amplifier 45 a whichsignal has passed through the double wave shorting circuit 43 a whileattenuated because of the loss at the double wave shorting circuit 43 aand has reached the drain end of the FET 42 a is the same as theamplitude of the signal of the frequency of the modulating wave includedin the amplified signal output from the drain end of the FET 42 a.

[0305] Therefore, the signal of the frequency of the modulating wavehaving reached the drain end of the FET 42 a and the signal of thefrequency of the modulating wave included in the amplified signal outputfrom the drain end of the FET 42 a are the same in amplitude andopposite in phase. Consequently, since these two signals of thefrequency of the modulating wave cancel each other out, intermodulationdistortion can be prevented from deteriorating due to the mixture of thesignal of the frequency of the modulating wave which is a second-orderintermodulation distortion component with the signal of the modulatedwave at the drain of the FET 42 b.

[0306] Likewise, the signal of the frequency of the modulating waveamplified by the inverting amplifier 45 b passes through the double waveshorting circuit 43 d to reach the drain end of the FET 42 c. Whenpassing through the double wave shorting circuit 43 d, the signal of thefrequency of the modulating wave is somewhat attenuated because of aloss at the double wave shorting circuit 43 d.

[0307] The gain of the inverting amplifier 42 b is previously adjustedso that the amplitude of the signal output from the inverting amplifier45 b after inverted and amplified by the inverting amplifier 45 b whichsignal has passed through the double wave shorting circuit 43 b whileattenuated because of the loss at the double wave shorting circuit 43 band has reached the drain end of the FET 42 c is the same as theamplitude of the signal of the frequency of the modulating wave includedin the amplified signal output from the drain end of the FET 42 c.

[0308] Therefore, the signal of the frequency of the modulating wavehaving reached the drain end of the FET 42 c and the signal of thefrequency of the modulating wave included in the amplified signal outputfrom the drain end of the FET 42 c are the same in amplitude andopposite in phase. Consequently, since these two signals of thefrequency of the modulating wave cancel each other out, third-orderintermodulation distortion can be prevented from deteriorating due tothe mixture of the signal of the frequency of the modulating wave whichis a second-order intermodulation distortion component with the signalof the modulated wave at the drain of the FET 42 c.

[0309] The amplified signals output from the drains of the FET 42 a andthe FET 42 c, like in the first embodiment, have their impedancesmatched and are combined with each other by the combiningcircuit/matching circuit 28, and are output to the output terminal 29.

[0310] As described above, in the power amplifier 62 of the presentembodiment, since the signals of the frequency of the modulating wavecancel each other out at the drain ends of the FET 42 a and the FET 42b, intermodulation distortion can be prevented from deteriorating due tothe mixture of the signal of the frequency of the modulating wave withthe signal of the frequency of the modulating wave at the drains.

[0311] Further, in the power amplifier 62 of the present embodiment,even when the signals of the frequency of the modulating wave areattenuated because of a loss at the double wave shorting circuits 43 a,43 b, 43 c and 43 d, since the signals of the frequency of themodulating wave are amplified by the inverting amplifiers 45 a and 45 b,the two signals of the frequency of the modulating wave can be made thesame in amplitude and opposite in phase at the drain ends of the FET 42a and the FET 42 b. Consequently, a low-distortion characteristic can beobtained in a wide band using the linearity of the FET 42 a and the likeas much as possible.

[0312] Further, by the FET size of the FET 42 b being smaller than thoseof the FET 42 a and the FET 42 c and increasing the gains of theinverting amplifiers 42 a and 42 b accordingly, the signal of thefrequency of the modulated wave input to the FET 42 b can be reduced, sothat the efficiency of the power amplifier 62 can be improved. Further,in such a case, the amplified signal output from the drain of the FET 42b is weaker than those output from the drains of the FET 42 a and theFET 42 c. Consequently, when the amplified signal of the FET 42 b isoutput from the output terminal 29 being combined with the amplifiedsignals output from the FET 42 a and the FET 42 c instead of beingterminated by the terminating resistor 48, the distortion componenthardly increases on average. Therefore, the amplified signal of the FET42 b may be output from the output terminal 29 being combined with theamplified signals output from the FET 42 a and the FET 42 c instead ofbeing terminated by the terminating resistor 48.

[0313]FIG. 8 shows an example in which the power amplifier 62 of thepresent embodiment is formed within a multilayer dielectric substrate.

[0314] On a dielectric substrate 91, the following are formed: thematching circuit/splitting circuit 41; the FETs 42 a, 42 b and 42 c; theinverting amplifiers 42 a and 45 b; the capacitors 27 a and 27 b whichare chip condensers; and the combining circuit/matching circuit 28.Below the dielectric substrate 91, a dielectric substrate 92 on which ashield electrode is formed is formed.

[0315] Below the dielectric substrate 92, a dielectric substrate 93 isformed. On the dielectric substrate 93, the double wave shortingcircuits 43 a, 43 b, 43 c and 43 d are formed. Between the dielectricsubstrate 93 and a grounded layer which is a shield electrode of adielectric substrate 94, the capacitors 44 a, 44 b, 46 a and 46 b areformed. Below the dielectric substrate 92, the dielectric substrate 94on which the shield electrode is formed is formed.

[0316] While the FET sizes of the FET 42 a and the FET 42 b are the samein the present embodiment, the present invention is not limited thereto.The FET sizes of the FET 42 a and the FET 42 c may be different. In thiscase, it is preferable that the FET size of the FET 42 b be smaller thanthe smaller one of the FET sizes of the FET 42 a and the FET 42 c.

[0317] Further, instead of the terminating resistor 48 of the presentembodiment, the following may be used: a terminating load comprising acombination of a capacitor, an inductor and a resistor; a terminatingload comprising a combination of a capacitor and a resistor; aterminating load comprising a combination of an inductor and a resistor;and a terminating load comprising a combination of a capacitor and aninductor.

[0318] Similar effects to those obtained from the present embodiment canbe obtained from a power amplifier in which the FET 42 c, the doublewave shorting circuits 43 c and 43 d, the inverting amplifier 45 b, thecapacitors 45 b and 46 b and the capacitor 27 b of the power amplifier62 of the second embodiment are not provided.

[0319] That is, in FIG. 4, the matching circuit/splitting circuit 41 isreplaced with a matching circuit/splitting circuit that splits the inputinto two, and the combining circuit/matching circuit 28 is replaced witha matching circuit that outputs the amplified signal having passedthrough the capacitor 27 a to the output terminal 29 and matches theimpedance thereof. Similar effects as those obtained from the presentembodiment can also be obtained by doing this.

[0320] Further, while in the inverting amplifier 62 of the secondembodiment, the FETs 42 a and 42 c whose amplified signals are output tothe output terminal are two in number and the FET 42 b for canceling outthe signal of the frequency of the modulating wave is one in number, thepresent invention is not limited thereto. The power amplifier may haveone FET for canceling out the signal of the frequency of the modulatingwave and a number (N−1) of FETs whose amplified signals are output tothe output terminal. In this case, to each of the gates of the number(N−1) of FETs, the corresponding output of a matching circuit/splittingcircuit that splits the signal of the frequency of the modulated waveinto a number N is connected. To the gate of the FET for canceling outthe signal of the frequency of the modulating wave, the remaining outputof the matching circuit/splitting circuit is connected. Between each ofthe number (N−1) of FETs and the FET for canceling out the signal of thefrequency of the modulating wave, a circuit having an equal structure tothat of the circuit part of the double wave shorting circuit 43 b, thecapacitor 46 a, the inverting amplifier 45 a, the capacitor 44 a, thedouble wave shorting circuit 43 a and the capacitor 27 a of FIG. 4 isconnected. Moreover, the signal output from each of the number (N−1) ofFETs passes through a capacitor, equivalent to the capacitor 27 a, ofeach FET and is output to the output terminal 29 from a combiningcircuit/matching circuit that combines a number (N−1) of inputs andmatches the impedances thereof.

[0321] Further, while in the present embodiment, at the drain of the FET42 b, the double wave shorting circuit 43 b and the double wave shortingcircuit 43 c are provided on the circuit lines reaching the FETs 42 aand 42 c, the present invention is not limited thereto. A structure maybe used such that one end of a double wave shorting circuit is connectedto the drain of the FET 42 b and the other end of the double waveshorting circuit is connected to the input of the inverting amplifier 45a and the input of the inverting amplifier 45 b. In such a poweramplifier, a number (N−1) of FETs whose amplified signals are output tothe output terminal may be provided as mentioned above. By doing this,the number of double wave shorting circuits can be reduced.

[0322] As described above, of the elements on the circuit lines reachingfrom the drain of the FET 42 b to the FETs 42 a and 42 c, the doublewave shorting circuit 43 b and the double wave shorting circuit 43 c maybe replaced with one common element, and further, all or some of theelements on the lines reaching from the drain of the FET 42 b to the FET42 a and the FET 42 c may be further replaced with one common element.

[0323] For example, the double wave shorting circuit 43 b and thecapacitor 46 a of the elements on the line reaching from the drain ofthe FET 42 b to the drain of the FET 42 a and the double wave shortingcircuit 43 c and the capacitor 36 c of the circuit part reaching fromthe drain of FET 42 b to the drain of the FET 42 c may each be replacedwith one common element. That is, one end of the double wave shortingcircuit is connected to the drain of the FET 42 b, and the output fromthe other end of the double wave shorting circuit is split into two by anon-illustrated splitting circuit. One of the two split outputs isconnected to the input of the inverting amplifier 42 a, and the otheroutput is connected to the input of the inverting amplifier 45 b.Moreover, to the other end of the double wave shorting circuit, one endof the capacitor replacing the capacitors 46 a and 46 b is connected,and the other end of the capacitor is grounded.

[0324] Moreover, for example, the double wave shorting circuit 43 b, thecapacitor 46 a and the inverting amplifier 45 a of the circuit part onthe line reaching from the drain of the FET 42 b to the drain of the FET42 a and the double wave shorting circuit 43 c, the capacitor 46 b andthe inverting amplifier 46 b of the circuit part on the line reachingfrom the drain of the FET 42 b to the drain of the FET 42 c may each bereplaced with one common element. That is, one end of the double waveshorting circuit is connected to the drain of the FET 42 b, one end ofthe capacitor and the input of the inverting amplifier are connected tothe other end of the double wave shorting circuit, the other end of thecapacitor is grounded, the input of a non-illustrated splitting circuitis connected to the output of the inverting amplifier, the output splitinto two by the slitting circuit is connected to the other end of thedouble wave shorting circuit 43 a and the other end of the double waveshorting circuit 43 d, and the capacitors 44 a and 44 b are connected tothe other ends of the double wave shorting circuits 43 a and 43 d.

[0325] Moreover, for example, the double wave shorting circuit 43 b, thecapacitor 46 a, the inverting amplifier 45 a and the capacitor 44 a ofthe circuit part reaching from the drain of the FET 42 b to the drain ofthe FET 42 a and the double wave shorting circuit 43 c, the capacitor 46b, the inverting amplifier 46 b and the capacitor 44 b of the circuitpart reaching from the drain of the FET 42 b to the drain of the FET 42c may each be replaced with one common element. That is, one end of thedouble wave shorting circuit is connected to the drain of the FET 42 b,one end of one of the capacitors and the input of the invertingamplifier are connected to the other end of the double wave shortingcircuit, the other end of the capacitor is grounded, the other capacitorand the input of a non-illustrated splitting circuit are connected tothe output of the inverting amplifier, the other end of the capacitor isgrounded, and the output split into two by the splitting circuit isconnected to the other end of the double wave shorting circuit 43 a andthe other end of the double wave shorting circuit 43 d.

[0326] Moreover, for example, the double wave shorting circuit 43 b, thecapacitor 46 a, the inverting amplifier 45 a, the capacitor 44 a and thedouble wave shorting circuit 43 a of the circuit part reaching from thedrain of the FET 42 b to the drain of the FET 42 a and the double waveshorting circuit 43 c, the capacitor 46 b, the inverting amplifier 46 b,the capacitor 44 b and the double wave shorting circuit 43 d of thecircuit part reaching from the drain of the FET 42 b to the drain of theFET 42 c may each be replaced with one common element. That is, one endof one of the double wave shorting circuits is connected to the drain ofthe FET 42 b, one end of one of the capacitors and the input of theinverting amplifier are connected to the other end of the double waveshorting circuit, the other end of the capacitor is grounded, the othercapacitor and the other end of the other double wave shorting circuitare connected to the output of the inverting amplifier, the input of anon-illustrated splitting circuit is connected to the other end of thedouble wave shorting circuit, and the output split into two by thesplitting circuit is connected to the drain of the FET 42 a and thedrain of the FET 42 c.

[0327] It is to be noted that in such a power amplifier, a number (N−1)of FETs whose amplified signals are output to the output terminal may beprovided as mentioned above.

[0328] Further, the power amplifier may comprise a combination of aplurality of power amplifiers described in the first embodiment and thesecond embodiment.

[0329] For example, that two power amplifiers 62 of FIG. 4 are combinedmeans that the matching circuits/splitting circuits 41 of the two poweramplifiers 62 are replaced with one common element. That is, that thematching circuits/splitting circuits 41 are replaced with one commonelement means that the two matching circuits/splitting circuits 41 arerealized as one matching circuit/splitting circuit. The common matchingcircuit/splitting circuit receives the signal of the frequency of themodulated wave through one input terminal 21 and splits the signal intosix. Of the six, three outputs are input to the FETs of one of the poweramplifiers 62, and the remaining three outputs are input to the FETs ofthe other power amplifier 62.

[0330] The combining circuits/matching circuits 28 are similarlyreplaced with one common element. That is, that the combiningcircuits/matching circuits 28 are replaced with one common element meansthat the two combining circuits/matching circuits 28 are realized as onecircuit. The common combining circuit/matching circuit 28 combines fouramplified signals and outputs the composite signal to one input terminal29, and matches the impedances thereof. The amplified signals havingpassed through the capacitors 27 a and 27 b of one of the poweramplifiers 62 are input to two inputs of the common combiningcircuit/matching circuit, and the amplified signals having passedthrough the capacitors 27 a and 27 b of the other power amplifier 62 areinput to the remaining two inputs of the common combiningcircuit/matching circuit 28. These four amplified signals are combinedby the common combining circuit/matching circuit, have their impedancesmatched, and are output from one output terminal 29.

[0331] By doing this, a power amplifier comprising a combination of aplurality of and/or a plurality of kinds of the following can also beobtained: the power amplifier 61 of the first embodiment; the poweramplifier 62 of the second embodiment; and the power amplifier which isa modification of the power amplifier 62 described in the secondembodiment. As the matching circuit/splitting circuit of the poweramplifier comprising a combination of a plurality of and/or a pluralityof kinds of power amplifiers of the embodiments as mentioned above, onecommon circuit replacing the matching circuits/splitting circuits of thecombined power amplifiers is used like in the description given above.Likewise, as the combining circuit/matching circuit of the poweramplifier comprising a plurality of and/or a plurality of kinds of poweramplifiers of the embodiments, one common circuit replacing thecombining circuits/matching circuits of the combined power amplifiers isused. As described above, similar effects to those obtained from theembodiments can be obtained from the power amplifiers comprising acombination of power amplifiers of the embodiments.

[0332] The FETs of the embodiments are an example of the amplifyingelements of the present invention. The double wave shorting circuits ofthe embodiments are an example of the filters of the present invention.The FET 23 a of the embodiment is an example of the first amplifyingelement of the present invention. The FET 23 b of the embodiment is anexample of the second amplifying element of the present invention. Thedouble wave shorting/bias choke circuit 24 a of the embodiment is anexample of the first filter of the present invention. The double waveshorting/bias choke circuit 24 b of the embodiment is an example of thesecond filter of the present invention. The FET 42 a of the embodimentis an example of the first amplifying element of the present invention.The FET 42 c of the embodiment is an example of the first amplifyingelement of the present invention. The FET 42 b of the embodiment is anexample of the second amplifying element of the present invention.

[0333] The amplifying elements of the present invention are not limitedto the FETs of the embodiments and may be other kinds of amplifyingelements such as transistors.

[0334] Further, examples of the radio communication apparatus of thepresent invention include mobile radio apparatuses such as portabletelephones, PHSs (personal handyphone systems), car telephones, trainradio telephones, maritime mobile radio telephones, aeronautical radiotelephones, cordless telephones and radio pagers, and base stationapparatuses thereof.

[0335] As is apparent from the description given above, the presentinvention is capable of providing a power amplifier, a power amplifyingmethod capable of reducing the impedance of the circuit part on theoutput side of the amplifying element at the frequency of the modulatingwave in a structure different from that of the conventional poweramplifier, and a radio communication apparatus.

[0336] Moreover, the present invention is capable of providing a poweramplifier,a power amplifying method capable of making lower theimpedance of the circuit part on the output side of the amplifyingelement at the frequency of the modulating wave and of more effectivelyusing the linearity of the amplifying element, and a radio communicationapparatus.

What is claimed is:
 1. A power amplifier comprising: a splitting circuitsplitting a signal of a frequency of a modulated wave into two; a firstamplifying element having its input connected to one output of saidsplitting circuit; a second amplifying element having its inputconnected to the other output of said splitting circuit; a combiningcircuit combining an output of said first amplifying element with anoutput of said second amplifying element to output a composite signal; afirst filter having one end connected to the output of said firstamplifying element, said first filter not allowing the signal of thefrequency of the modulated wave to pass therethrough and allowing asignal of a frequency band of a modulating wave of the signal of thefrequency of the modulated wave to pass therethrough; a second filterhaving one end connected to the output of said second amplifyingelement, said second filter not allowing the signal of the frequency ofthe modulated wave to pass therethrough and allowing the signal of thefrequency band of the modulating wave of the signal of the frequency ofthe modulated wave to pass therethrough; and an phase inverting circuitconnected between the other end of said first filter and the other endof said second filter, said phase inverting circuit allowing the signalof the frequency band of the modulating wave to pass therethrough whileinverting a phase of the signal of the frequency of the modulating wave.2. A power amplifier according to claim 1, wherein said phase invertingcircuit comprises an inductor and a capacitor.
 3. A power amplifieraccording to claim 2, wherein said phase inverting circuit comprises: aninductor having one end connected to the other end of said first filterand having its other end connected to the other end of said secondfilter; a first capacitor having one end connected to one end of saidinductor and having its other end grounded; and a second capacitorhaving one end connected to the other end of said inductor and havingits other end grounded, and wherein one end of said phase invertingcircuit is one end of said inductor, and the other end of said phaseinverting circuit is the other end of said inductor.
 4. A poweramplifier according to claim 1, further comprising a bias choke circuitconnected at least one of said first filter, said second filter and saidphase inverting circuit, said bias choke circuit supplying a biasvoltage.
 5. A power amplifier according to claim 2, wherein said phaseinverting circuit comprises: a first inductor; a second inductor; afirst capacitor; a second capacitor; and a third capacitor, wherein saidfirst inductor has one end connected to the other end of said firstfilter and has its other end connected to one end of said secondinductor, said second inductor has its other end connected to the otherend of said second filter, said first capacitor has one end connected tothe one end of said first inductor and has its other end grounded, saidsecond capacitor has one end connected to the other end of said firstinductor and has its other end grounded, and said third capacitor hasone end connected to the other end of said second inductor and has itsother end grounded, and wherein one end of said phase inverting circuitis one end of said first inductor and the other end of said phaseinverting circuit is the other end of said second inductor.
 6. A poweramplifier according to claim 5, wherein said phase inverting circuitcomprises: a fourth inductor having one end connected to a bias supplyand having its other end connected to the other end of said firstinductor; and a fourth capacitor connected to one end of said fourthinductor and having its other end grounded.
 7. A power amplifiercomprising: a splitting circuit splitting a signal of a frequency of amodulated wave into at least two; a first amplifying element having itsinput connected to one output of said splitting circuit; a secondamplifying element having its input connected to the other output ofsaid splitting circuit; a first filter having one end connected to anoutput of said first amplifying element, said first filter not allowingthe signal of the frequency of the modulated wave to pass therethroughand allowing a signal of a frequency band of a modulating wave of themodulated wave to pass therethrough; a second filter having one endconnected to an output of said second amplifying element, said secondfilter not allowing the signal of the frequency of the modulated wave topass therethrough and allowing the signal of the frequency band of themodulating wave to pass therethrough; and an inverting amplifier havingits output connected to the other end of said first filter and havingits input connected to the other end of the second filter, saidinverting amplifier amplifying the signal of the frequency band of themodulating wave while inverting a phase of the signal of the frequencyband of the modulating wave, wherein at least said output of said firstamplifying element is output to an outside.
 8. A power amplifiercomprising: a splitting circuit splitting a signal of a frequency of amodulated wave into a number N (N is an integer not less than 3); anumber (N−1) of first amplifying elements having their inputs connectedto a number (N−1) of outputs of a number N of outputs of said splittingcircuit; a second amplifying element having its input connected to anoutput of said splitting circuit other than the number (N−1) of outputsof said splitting circuit; a first filter having one end connected toinputs of a (N−1) splitting circuit splitting its input into a number(N−1) and having their outputs connected to outputs of said number (N−1)of first amplifying elements, said first filter not allowing the signalof the frequency of the modulated wave to pass therethrough and allowinga signal of a frequency band of a modulating wave of the modulated waveto pass therethrough; a second filter having one end connected to anoutput of said amplifying element, said second filter not allowing thesignal of the frequency of the modulated wave to pass therethrough andallowing the signal of the frequency band of the modulating wave to passtherethrough; an inverting amplifier having its input connected to theother end of said second filter and having its output connected to theother end of said first filter, said inverting amplifier amplifying thesignal of the frequency band of the modulating wave while inverting aphase of the signal of the frequency band of the modulating wave; and acombining circuit combining at least the outputs of said number (N−1) offirst amplifying elements to output a composite signal.
 9. A poweramplifier comprising: a splitting circuit splitting a signal of afrequency of a modulated wave into a number N (N is an integer not lessthan 3); a number (N−1) of first amplifying elements having their inputsconnected to a number (N−1) of outputs of a number N of outputs of thesplitting circuit; a second amplifying element having its inputconnected to an output of said splitting circuit other than the number(N−1) of outputs of said splitting circuit; a number (N−1) of firstfilters having one ends connected to outputs of said number (N−1) offirst amplifying elements, said first filters not allowing the signal ofthe frequency of the modulated wave to pass therethrough and allowing asignal of a frequency band of a modulating wave of the modulated wave topass therethrough; a second filter having one end connected to an outputof said second amplifying element, said second filter not allowing thesignal of the frequency of the modulated wave to pass therethrough andallowing the signal of the frequency band of the modulating wave to passtherethrough; an inverting amplifier having its input connected to theother end of said second filter, said inverting amplifier amplifying thesignal of the frequency band of the modulating wave while inverting aphase of the signal of the frequency band of the modulating wave; and acombining circuit combining at least the outputs of said number (N−1) offirst amplifying elements to output a composite signal, wherein saidother ends of said number (N−1) of first filters are connected to thenumber (N−1) of outputs of a (N−1) splitting circuit splitting its inputinto a number (N−1) and connected to an output of said invertingamplifier.
 10. A power amplifier comprising: a splitting circuitsplitting a signal of a frequency of a modulated wave into a number N (Nis an integer not less than 3); a number (N−1) of first amplifyingelements having their inputs connected to a number (N−1) of outputs of anumber N of outputs of said splitting circuit; a second amplifyingelement having its input connected to an output of said splittingcircuit other than the number (N−1) of outputs of said splittingcircuit; a number (N−1) of first filters having one ends connected tooutputs of said number (N−1) of first amplifying elements, said firstfilters not allowing the signal of the frequency of the modulated waveto pass therethrough and allowing a signal of a frequency band of amodulating wave of the modulated wave to pass therethrough; a secondfilter having one end connected to an output of said second amplifyingelement, said second filter not allowing the signal of the frequency ofthe modulated wave to pass therethrough and allowing the signal of thefrequency band of the modulating wave to pass therethrough; a number(N−1) of inverting amplifiers having their outputs connected to theother ends of said number (N−1) of first filters and having their inputsconnected to the number (N−1) of outputs of a (N−1) splitting circuitsplitting its input into a number (N−1) and having their inputsconnected to the other end of said second filter, said invertingamplifiers amplifying the signal of the frequency band of the modulatingwave while inverting a phase of the signal of the frequency band of themodulating wave; and a combining circuit combining at least the outputsof said number (N−1) of first amplifying elements to output a compositesignal.
 11. A power amplifier comprising: a splitting circuit splittinga signal of a frequency of a modulated wave into a number N (N is aninteger not less than 3); a number (N−1) of first amplifying elementshaving their inputs connected to a number (N−1) of outputs of a number Nof outputs of said splitting circuit; a second amplifying element havingits input connected to an output of said splitting circuit other thanthe number (N−1) of outputs of said splitting circuit; a number (N−1) offirst filters having one ends connected to outputs of said number (N−1)of first amplifying elements, said first filters not allowing the signalof the frequency of the modulated wave to pass therethrough and allowinga signal of a frequency band of a modulating wave of the modulated waveto pass therethrough; a number (N−1) of inverting amplifiers havingtheir outputs connected to the other ends of said number (N−1) of firstfilters, said inverting amplifiers amplifying the signal of thefrequency band of the modulating wave while inverting a phase of thesignal of the frequency band of the modulating wave; a number (N−1) ofsecond filters having one end connected to inputs of said number (N−1)of inverting amplifiers and having its other end connected to the number(N−1) of outputs of a (N−1) splitting circuit splitting its input into anumber (N−1) and connected to an output of said second amplifyingelement, said second filters not allowing the signal of the frequency ofthe modulated wave to pass therethrough and allowing the signal of thefrequency band of the modulating wave to pass therethrough; and acombining circuit combining at least the outputs of said number (N−1) offirst amplifying elements to output a composite signal.
 12. A poweramplifier according to any one of claims 7 to 11, wherein said output ofsaid second amplifying element is terminated.
 13. A power amplifieraccording to claim 12, wherein that said output of said secondamplifying element is terminated means that a terminating resistor isconnected to the output of said second amplifying element or that aterminating load comprising a capacitor and/or an inductor is connectedto the output of said second amplifying element.
 14. A power amplifieraccording to any one of claims 7 to 11, wherein said second amplifyingelement is smaller in amplifying element size than said first amplifyingelement.
 15. A power amplifier comprising a plurality of poweramplifiers according to any one of claims 1 to 6 and 8 to 11, whereinsaid splitting circuits of said power amplifiers are replaced with onecommon element, and the same signal of the frequency of the modulatedwave is input, and wherein said combining circuits of said poweramplifiers are replaced with one common element, and outputs one outputsignal generated by signal combination.
 16. A power amplifiercomprising: a plurality of power amplifiers according to claim 7; and acombining circuit generating by signal combination an output to beoutput to an outside of said power amplifiers, and outputting theoutput, wherein said splitting circuits of said power amplifiers arereplaced with one common element, and the same signal of the frequencyof the modulated wave is input.
 17. A power amplifier having amultilayer dielectric substrate where the power amplifier according toany one of claims 1 to 11 is formed.
 18. A power amplifier according toclaim 17, wherein said multilayer dielectric substrate comprises: asemiconductor substrate disposed thereabove; and a multilayer dielectricsubstrate disposed below said semiconductor substrate.
 19. A poweramplifier according to claim 18, comprising an internal matchingsubstrate in which said multilayer dielectric substrate is disposed. 20.A power amplifier according to any one of claims 1 to 11, wherein afrequency of the signal of the frequency of the modulated wave is notmore than a thousand times a frequency band of the signal of thefrequency band of the modulating wave.
 21. A power amplifier accordingto any one of claims 1 to 11, wherein said first filter and said secondfilter allow a harmonic component of the signal of the frequency of themodulating wave to pass therethrough.
 22. A radio communicationapparatus having at least a transmitting circuit outputting atransmission wave, wherein said power amplifier according to any one ofclaims 1 to 11 is used for said transmitting circuit.
 23. A poweramplifying method comprising the steps of: a splitting step splitting asignal of a frequency of a modulated wave into two; a first amplifyingstep having its input connected to one output of said splitting step andamplifying its input; a second amplifying step having its inputconnected to the other output of said splitting step and amplifying itsinput; a combining step combining an output of said first amplifyingstep with an output of said second amplifying step to output a compositesignal; a first filtering step having one end connected to the output ofsaid first amplifying step, said first filtering step not allowing thesignal of the frequency of the modulated wave to pass therethrough andallowing a signal of a frequency band of a modulating wave of the signalof the frequency of the modulated wave to pass therethrough; a secondfiltering step having one end connected to the output of said secondamplifying step, said second filtering step not allowing the signal ofthe frequency of the modulated wave to pass therethrough and allowingthe signal of the frequency band of the modulating wave of the signal ofthe frequency of the modulated wave to pass therethrough; and an phaseinverting step connected between the other end of said first filteringstep and the other end of said second filtering step, said phaseinverting step allowing the signal of the frequency band of themodulating wave to pass therethrough while inverting a phase of thesignal of the frequency of the modulating wave.
 24. A power amplifyingmethod comprising the steps of: a splitting step splitting a signal of afrequency of a modulated wave into at least two; a first amplifying stephaving its input connected to one output of said splitting step andamplifying its input; a second amplifying step having its inputconnected to the other output of said splitting step and amplifying itsinput; a first filtering step having one end connected to an output ofsaid first amplifying step, said first filtering step not allowing thesignal of the frequency of the modulated wave to pass therethrough andallowing a signal of a frequency band of a modulating wave of themodulated wave to pass therethrough; a second filtering step having oneend connected to an output of said second amplifying step, said secondfiltering step not allowing the signal of the frequency of the modulatedwave to pass therethrough and allowing the signal of the frequency bandof the modulating wave to pass therethrough; and an inverting amplifyingstep having its output connected to the other end of said firstfiltering step and having its input connected to the other end of thesecond filtering step, said inverting amplifying step amplifying thesignal of the frequency band of the modulating wave while inverting aphase of the signal of the frequency band of the modulating wave,wherein at least said output of said first amplifying step is output toan outside.
 25. A power amplifying method comprising the steps of: asplitting step splitting a signal of a frequency of a modulated waveinto a number N (N is an integer not less than 3); a number (N−1) offirst amplifying steps having their inputs connected to a number (N−1)of outputs of a number N of outputs of said splitting step andamplifying their inputs; a second amplifying step having its inputconnected to an output of said splitting step other than the number(N−1) of outputs of said splitting step and amplifying its input; afirst filtering step having one end connected to inputs of a (N−1)splitting step splitting its input into a number (N−1) and having theiroutputs connected to outputs of said number (N−1) of first amplifyingsteps, said first filter not allowing the signal of the frequency of themodulated wave to pass therethrough and allowing a signal of a frequencyband of a modulating wave of the modulated wave to pass therethrough; asecond filtering step having one end connected to an output of saidamplifying step, said second filtering step not allowing the signal ofthe frequency of the modulated wave to pass therethrough and allowingthe signal of the frequency band of the modulating wave to passtherethrough; an inverting amplifying step having its input connected tothe other end of said second filtering step and having its outputconnected to the other end of said first filtering step, said invertingamplifying step amplifying the signal of the frequency band of themodulating wave while inverting a phase of the signal of the frequencyband of the modulating wave; and a combining step combining at least theoutputs of said number (N−1) of first amplifying steps to output acomposite signal.
 26. A power amplifying method comprising the steps of:a splitting step splitting a signal of a frequency of a modulated waveinto a number N (N is an integer not less than 3); a number (N−1) offirst amplifying steps having their inputs connected to a number (N−1)of outputs of a number N of outputs of the splitting circuit andamplifying their inputs; a second amplifying step having its inputconnected to an output of said splitting step other than the number(N−1) of outputs of said splitting step and amplifying its input; anumber (N−1) of first filtering steps having one ends connected tooutputs of said number (N−1) of first amplifying steps, said firstfiltering steps not allowing the signal of the frequency of themodulated wave to pass therethrough and allowing a signal of a frequencyband of a modulating wave of the modulated wave to pass therethrough; asecond filtering step having one end connected to an output of saidsecond amplifying step, said second filtering step not allowing thesignal of the frequency of the modulated wave to pass therethrough andallowing the signal of the frequency band of the modulating wave to passtherethrough; an inverting amplifying step having its input connected tothe other end of said second filtering step, said inverting amplifyingstep amplifying the signal of the frequency band of the modulating wavewhile inverting a phase of the signal of the frequency band of themodulating wave; and a combining step combining at least the outputs ofsaid number (N−1) of first amplifying steps to output a compositesignal, wherein said other ends of said number (N−1) of first filteringstep are connected to the number (N−1) of outputs of a (N−1) splittingstep splitting its input into a number (N−1) and connected to an outputof said inverting amplifying step.
 27. A power amplifying methodcomprising the steps of: a splitting step splitting a signal of afrequency of a modulated wave into a number N (N is an integer not lessthan 3); a number (N−1) of first amplifying steps having their inputsconnected to a number (N−1) of outputs of a number N of outputs of saidsplitting circuit and amplifying their inputs; a second amplifying stephaving its input connected to an output of said splitting circuit otherthan the number (N−1) of outputs of said splitting circuit andamplifying its input; a number (N−1) of first filtering steps having oneends connected to outputs of said number (N−1) of first amplifyingsteps, said first filtering steps not allowing the signal of thefrequency of the modulated wave to pass therethrough and allowing asignal of a frequency band of a modulating wave of the modulated wave topass therethrough; a second filtering step having one end connected toan output of said second amplifying step, said second filtering step notallowing the signal of the frequency of the modulated wave to passtherethrough and allowing the signal of the frequency band of themodulating wave to pass therethrough; a number (N−1) of invertingamplifying steps having their outputs connected to the other ends ofsaid number (N−1) of first filtering steps and having their inputsconnected to the number (N−1) of outputs of a (N−1) splitting stepsplitting its input into a number (N−1) and having their inputsconnected to the other end of said second filter, said invertingamplifying step amplifying the signal of the frequency band of themodulating wave while inverting a phase of the signal of the frequencyband of the modulating wave; and a combining step combining at least theoutputs of said number (N−1) of first amplifying steps to output acomposite signal.
 28. A power amplifying step comprising the steps of: asplitting step splitting a signal of a frequency of a modulated waveinto a number N (N is an integer not less than 3); a number (N−1) offirst amplifying steps having their inputs connected to a number (N−1)of outputs of a number N of outputs of said splitting step andamplifying their inputs; a second amplifying step having its inputconnected to an output of said splitting step other than the number(N−1) of outputs of said splitting step and amplifying its input; anumber (N−1) of first filtering steps having one ends connected tooutputs of said number (N−1) of first amplifying steps, said firstfiltering steps not allowing the signal of the frequency of themodulated wave to pass therethrough and allowing a signal of a frequencyband of a modulating wave of the modulated wave to pass therethrough; anumber (N−1) of inverting amplifying steps having their outputsconnected to the other ends of said number (N−1) of first filteringsteps, said inverting amplifying steps amplifying the signal of thefrequency band of the modulating wave while inverting a phase of thesignal of the frequency band of the modulating wave; a number (N−1) ofsecond filtering steps having one end connected to inputs of said number(N−1) of inverting amplifying step and having its other end connected tothe number (N−1) of outputs of a (N−1) splitting step splitting itsinput into a number (N−1) and connected to an output of said secondamplifying element, said second filtering steps not allowing the signalof the frequency of the modulated wave to pass therethrough and allowingthe signal of the frequency band of the modulating wave to passtherethrough; and a combining step combining at least the outputs ofsaid number (N−1) of first amplifying steps to output a compositesignal.